[2][3] His notable designs include the main building of the University of Iceland, the National Theatre of Iceland, the Landakot Roman Catholic Cathedral in Reykjavík, and the Church of Akureyri.
[2] During this time, Guðjón was commissioned to plan the major buildings constructed by the Icelandic state.
Guðjón's design of Hallgrímskirkja was, for instance, inspired by basalt columns, such as those at Svartifoss.
[2] Many Icelandic church designs are influenced by those of Guðjón, and blend naturalism with modernism.
[3] A retrospective exhibition of Guðjón's work was held at the Hafnarborg in Hafnarfjördur in 2019-2020, on the centenary of his graduation (1919) and appointment as state architect (1920).